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Allied Telesis x908, X8100 manual Filter out a range of different prefix lengths

Models: X8100 x908

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Filter out a range of different prefix lengths

BGP: Configuring Prefix Filters

awplus(config-router)#neighbor 45.45.45.46 prefix-list list1 in

4.Shut down the neighbor, and then bring it up again.

awplus(config-router)#neighbor 45.45.45.46 shutdown awplus(config-router)#neighbor 45.45.45.46 no shutdown

5.Check that the IP route table now contains one of the routes learnt from that neighbor, but not the other.

awplus(config-router)# do show ip route

Codes: C - connected, S - static, R - RIP, B - BGP O - OSPF, IA - OSPF inter area

N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2

* - candidate default

B45.0.0.0/8 [20/0] via 45.45.45.46, vlan1, 00:00:06

C45.45.45.0/24 is directly connected, vlan1

C 64.0.0.0/4 is directly connected, vlan64

Filter out a range of different prefix lengths

This example filters out routes to 45.0.0.0 with prefix lengths in the range 5-8, accepts routes to 52.0.0.0/8, and implicitly filters out all other BGP routes.

1. Remove the existing prefix list entry.

awplus(config)# no ip prefix-list list1 permit 45.0.0.0/8

2.Add the following prefix list entries.

awplus(config)# ip prefix-list list1 deny 45.0.0.0/4 ge 5 le 8 awplus(config)# ip prefix-list list1 permit 52.0.0.0/8

3. Set that prefix list as the prefix list filter for neighbor 45.45.45.46

awplus(config)# router bgp 34567

awplus(config)# neighbor 45.45.45.46 prefix-list list2 in

4.Shut down the neighbor, and then bring it up again.

awplus(config-router)#neighbor 45.45.45.46 shutdown awplus(config-router)#neighbor 45.45.45.46 no shutdown

Page 24 Use Route Maps and Other Filters to Filter and Alter BGP and OSPF Routes

Image 24

Allied Telesis x908, X8100 manual Filter out a range of different prefix lengths

Contents

Introduction Technical GuideContents IntroductionWhich products and software version does it apply to? BGP Applying Route Maps to Imported RoutesRelated How To Notes Which products and software version does it apply to?BGP updates BGP Concepts and TerminologyBGP peers Update attributes OriginAS-path Next-hopAccess Control List ACL filters BGP Overview of the Available Filter TypesFilter types Distribute filtersExamples for filtering BGP Update messages Difference and Relationship in BGPHierarchy of the Different Filters BGP Example Example Distribute filters on page  Example AS path filters on page  Example Prefix filters on pageBasic configuration Confirming the neighbor relationship AlliedWare switchAlliedWare Plus switch awplus#show ip routeBGP Configuring Distribute Filters About ACLsUsing ACLs as filters Example Distribute filtersFilter out one particular route from a neighbor Filter out a range of prefix lengths awplusconfig# neighbor 45.45.45.46 distribute-list list2 in awplusconfig-router# do show ip routeawplusconfig# router bgp 3. Check that the IP route table now includes all the routesUse a numbered ACL instead of a named ACL awplusconfig-router# do show ip route 4. Check that the IP route table no longer includes 52.0.0.0/8BGP Configuring AS Path Filters AS path listsUsing AS path lists as path filters Example AS path filtersDiscard or allow routes from a neighbor 4. Shut down the neighbor, and then bring it up again a neighbor7. Shut down the neighbor, and then bring it up again Another example An outgoing filter that uses an AS-path listBGP Configuring AS Path Filters BGP Configuring Prefix Filters About prefix listsMask length Using prefix lists as prefix filters Example Prefix filtersawplusconfig-router# neighbor neighbor prefix-list list-name in awplusconfig-router# neighbor neighbor prefix-list list-name outFilter out a range of different prefix lengths BGP Configuring Prefix Filters awplusconfig-router# do show ip routeBGP Configuring Route Maps Structure of a route mapConfiguring a match clause ClausesAn AS path list A community list CaseCase One or more prefixes, by using a prefix list One or more prefixes, by using an ACLConfiguring a set clause A next hop addressAn origin A metric the MED attributeset community community-values additive set weight set atomic-aggregateset extcommunity rtsoo ext-comm-number set ip next-hop ipaddThe effect of different combinations of clauses One match clause with an actionNo match clause and one or more set clauses A match clause and one or more set clausesUpdate from Peer Update 1 to PeerUpdate 2 to Peer Router ASFirst, enter BGP router mode for the AS. The prompt should look like Examples Example B Match on a prefix-list that denies an entryawplusconfig#ip prefix-list test1 permit 52.0.0.0/8 awplusconfig-route-map#set metric4. Apply this route map as the in route map on the neighbor Example D Matching on a next-hop prefix-list Example E Prepending AS numbersawplusconfig-route-map#match ip address awplusconfig-route-map#router bgp1. Configure the AW peer to send out a community number The routes coming from that peer has communityadd ip routem=com entry=1 set commmun=8989 set bgp peer=45.45.45.45 outroutemap=com sendcommunity=yesBGP#show ip route set bgp peer=45.45.45.45 outroutemap=mixed sendcommunity=yes 8. Add that ACL as a distribute-list in-filter on the neighbor route-map marker permit Examples ACLs Path filters Prefix filters Route mapsBGP Applying Route Maps to Imported Routes Syntaxneighbor default-originate Other Uses of Route Mapsneighbor unsuppress-map networkBGP configuration Route map configurationBGP Route Map Filtering Example set local-preference route-map outdef permit OSPF Configuring Route Maps for Filtering and Modifying OSPF Routes MetricInterface Configuring a match clauseA prefix, by using a prefix list A prefix, by using an ACLExternal route type Configuring a set clauseOSPF Applying Route Maps  Set the metric, by using the command set metric